JPH07286602A - Pressure oil supply device - Google Patents

Abstract

PURPOSE:To improve inching operability by providing a pressure reducing valve section which relatively reduce the discharge amount of a pump in an initial operation period in a device to supply the discharge pressure oil from a variable displacement type hydraulic pump to an actuator. CONSTITUTION:A pressure oil supply device is provided with a variable displacement type hydraulic pump 1 whose discharge amount is controlled by the load pressure of a load pressure detection passage 27, a pressure compensation valve 4 comprising a check valve section 2 and a pressure reducing valve section 3 and a direction control valve 5 and is also provided with a first pressure chamber 10 energizing a spool 15 to a first position side by load pressure. It is also provided with a pressure chamber 31 energizing the spool 15 to a second position side by pump discharge pressure, communicated to a pump discharge passage 24 through a throttle 32 for damping, a pressure chamber 31 energizing the spool 15 to a second position side by pump discharge pressure, communicated to the load pressure detection passage 27 through a throttle 32 for damping, and a second pressure chamber 11 energizing the spool 15 to a second position side by pump discharge pressure, communicated to the load pressure detection passage 27 through a throttle 32 for damping. The speed of an actuator 6 when it starts to move is made lower with the discharge amount from the pump made smaller than the value corresponding to load pressure at the initial time of operating the direction control valve 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure oil supply device for supplying discharge pressure oil of a variable displacement hydraulic pump to an actuator.

[0002]

2. Description of the Related Art A pressure oil supply device disclosed in Japanese Patent Application No. 4-161920 is known. That is, as shown in FIG. 1, a variable displacement hydraulic pump 1 (hereinafter referred to as variable hydraulic pump 1), a pressure compensating valve 4 including a check valve portion 2 and a pressure reducing valve portion 3, a directional control valve 5, and an actuator 6 are provided. The check valve unit 2 has a spool 9 that connects and disconnects the inlet port 7 and the outlet port 8, and the pressure reducing valve unit 3 communicates with the first port 13 and the second port 14 by the pressure of the first pressure chamber 10. The pressure of the second pressure chamber 11 and the weak spring 12
Has a spool 15 which is pushed in a direction to shut off the first port 13 and the second port 14 by the directional control valve 5 includes a pump port 16 and first and second load pressure detection ports 17, 1.
8, first and second actuator ports 19, 20, first
-Has a spool 23 that connects and disconnects the second tank ports 21 and 22.

The pump discharge passage 24 of the variable hydraulic pump 1 communicates with the inlet port 7 and the first port 13, and the swash plate 2
Directional control valve 2 for pump adjustment that tilts 5 to control capacity
6 communicates with the second port 14 via the load pressure detection path 27,
The outlet port 8 communicates with the pump port 16, the first pressure chamber 10 communicates with the first and second load pressure detection ports 17 and 18, and the second pressure chamber 11 communicates with the second port 14 through the throttle 28. A free piston 30 is fitted into a blind hole 29 of the spool 15 to form a pressure chamber 31, and the pressure chamber 31 is communicated with a slit-shaped opening 33 by a damper diaphragm 32.

With such a pressure oil supply device, when the spool 23 of the directional control valve 5 is in the neutral position shown in the drawing, the pressure reducing valve section 3 is used.
The spool 15 is pushed to the left by the weak spring 12 to push the spool 9 of the check valve portion 2 in the closing direction. on the other hand,
The pump discharge pressure is controlled by the pump adjusting directional control valve 26 from the pressure in the load pressure detection path 27 by a predetermined differential pressure, for example, 20 kg /
The pressure becomes higher by cm ² , and in this case the load pressure detection path 2
Since the pressure of 7 is zero, the pump discharge pressure is 20 kg / c
It becomes m ² . Then, the spool 9 of the check valve unit 2 is pushed to the right by the pressure of the inlet port 7 and opened, and is pushed to the left when the pressure of the outlet port 8 reaches 20 kg / cm ^2, and is closed.

From the state of FIG. 1, the spool 2 of the directional control valve 5
3 in the direction of the arrow to connect the pump port 16 to the second load pressure detection port 18 and the first load pressure detection port 17 to the first actuator 19, and the second actuator port 20 to the second tank port 22. At the first pressure oil supply position, the discharge pressure oil of the variable hydraulic pump 1 is supplied to the actuator 6 and rises to a pressure commensurate with the external load.

The pressure of the actuator 6, that is, the load pressure, flows into the first pressure chamber 10 and pushes the spool 15 to the right to communicate the first port 13 and the second port 14 with the opening 33 so that the pump discharge pressure is the first. The first port 13, the opening 33, the second port 14, and the throttle 28 flow into the second pressure chamber 11 to push the spool 15 in a direction to shut off the first port 13 and the second port 14, and at the same time, to the load pressure detection path 27. The load pressure is introduced to increase the discharge amount of the variable hydraulic pump 1.

That is, the pressure reducing valve section 3 is provided in the first pressure chamber 10
The pump discharge passage 24 and the second pressure chamber 11 are communicated until the pressure in the second pressure chamber 11 becomes equal to the pressure in the second pressure chamber 11. If the pressures in the first and second pressure chambers 10, 11 become equal, the weak spring 1
The pump discharge passage 24 and the second pressure chamber 11 are closed by 2 and brought into contact with the check valve portion 2. As a result, the load pressure detection path 27
The pressure inside is equal to the load pressure, and the pump discharge pressure is higher than the pressure inside the load pressure detection path 27 by a certain differential pressure (here 20 kg / cm ² ) by the pump adjusting directional control valve 26. Controlled by. This pump discharge pressure is guided to the pump port 16 via the check valve unit 2, that is, the inlet pressure and the outlet pressure (=) of the directional control valve 5 (=
During the load pressure, the differential pressure (= 20 kg / cm ² ) is maintained. Therefore, the flow rate supplied to the actuator 6 is controlled only by the change in the opening area of the throttle between the inlet side and the outlet side due to the stroke of the directional control valve 5.

In the above operation, when the spool 15 moves to the right due to the load pressure in the first pressure chamber 10, the pressure chamber 31
Since the pressure oil inside is discharged to the first port 3 side through the damper throttle 32, the spool 15 moves slowly to the right due to the pressure oil flow.

To this end, the spool 23 of the directional control valve 5
Is moved to the right to the first pressure oil supply position, the first port 13 and the second port 14 are gradually communicated with each other, and the pressure in the load pressure detection path 27 is gradually increased. The amount increases slowly and the actuator 6 operates slowly.

On the other hand, the spool 15 of the pressure reducing valve unit 3
If the pressure chamber 31 and the damper throttle 32 are not provided in the spool 15, the spool 15 suddenly moves to the right, the pressure in the load pressure detection path 27 rises sharply, and the discharge amount of the variable hydraulic pump 1 sharply increases. The actuator 6 suddenly operates.

[0011]

With the above-described pressure oil supply device, the actuator 6 can be operated slowly when the spool 23 of the directional control valve 5 is moved from the neutral position to the pressure oil supply position, and the spool 23 is neutralized. There is no problem when a large stroke is moved from the position toward the pressure oil supply position to increase the meter-in opening area, that is, when a large amount of pressure oil is supplied to the actuator 6.

However, the spool 2 of the directional control valve 5
When 3 is moved slightly from the neutral position toward the pressure oil supply position to make the meter-in opening area small, that is, when a small amount of pressure oil is supplied to the actuator 6 and the actuator 6 is slightly moved (inching operation), for example, When supplying pressure oil to the turning hydraulic motor of the hydraulic excavator to position and stop the upper body at a predetermined position, or when positioning the boom to raise when skiving, the actuator movement is
It is desirable that the change in the supply flow rate to the actuator be small with respect to the increase in the meter-in opening area of the directional control valve 5 in order to easily perform the work that requires the inching operation.

However, with the above-described structure, the spool 15 constituting the pressure reducing valve portion 3 of the pressure compensating valve 4 slowly moves to the right and the discharge amount of the variable hydraulic pump 1 slowly increases, so the inching operation described above is performed. However, the discharge amount of the variable hydraulic pump 1 becomes a value commensurate with the load pressure with the passage of time in the state where the spool 23 of the directional control valve 5 is moved by a slight stroke, and the actuator has a meter-in opening area of the directional control valve. Since the required flow rate is supplied, the inching operability becomes poor because the movement of the actuator becomes fast after some time elapses during the inching operation.

That is, the spool 15 of the pressure reducing valve section 3 described above.
After a certain period of time elapses even if the movement to the right of is slowed down, the first port 13 and the second port 14 communicate with each other and the same pressure as the load pressure applied to the first pressure chamber 10 is output to the load pressure detection path 27. Therefore, since the discharge amount of the variable hydraulic pump 1 becomes a flow rate commensurate with its load pressure, when the actuator 6 is supplied with a flow rate proportional to the meter-in opening area by the spool 23 of the directional control valve 5 and the actuator 6 is inching operated. After some time, the speed of the actuator increases, making it difficult to perform the work required for the inching operation.

Therefore, an object of the present invention is to provide a pressure oil supply device capable of solving the above problems.

[0016]

A first aspect of the present invention is directed to a variable displacement hydraulic pump 1 whose discharge amount is controlled by the load pressure of a load pressure detection path 27, a pressure composed of a check valve portion 2 and a pressure reducing valve portion 3. A compensating valve 4 and a direction control valve 5 for supplying pump discharge pressure oil to the actuator 6 are provided, and the check valve unit 2 connects the pump discharge passage 24 of the variable displacement hydraulic pump 1 and the pump port 16 of the direction control valve 5. -The spool 9 for shutting off is provided, and the pressure reducing valve portion 3 is pushed by the load pressure of the actuator 6 toward the first position communicating the pump discharge passage 24 and the load pressure detecting passage 27, and the weak spring 12 and the load. The pump discharge passage 24 and the load pressure detection passage 27 are shut off by the load pressure of the pressure detection passage 27, and the spool 15 pushed toward the second position for pushing the spool 9 of the check valve portion 2 in the closing direction is provided. Spoo 15 is a bleed that moves slowly from the second position to the first position, and at a position intermediate between the second position and the first position, a part of the pressure oil from the pump discharge passage 24 flows out to the tank. A pressure oil supply device having an off circuit. A second aspect of the present invention is a variable displacement hydraulic pump 1 whose discharge amount is controlled by the load pressure of the load pressure detection path 27,
The neutral position is switched to the pressure oil supply position by the operation command to supply the pump discharge pressure oil to the actuator 6, and the meter-in opening area of the directional control valve 5 is proportional to the operation command.
A pressure compensating valve 4 that is pushed in the opening direction by the pump discharge pressure and is pushed in the closing direction by the load pressure of the actuator 6 to make the primary side pressure a pressure commensurate with the load pressure; and the load pressure detection path 2
Bleed-off circuit 61 connected to No. 7 and a bleed-off position provided in this bleed-off circuit 61, which is a bleed-off position when the magnitude of the operation command is an intermediate magnitude, and a shut-off position when the magnitude of the operation instruction is other than the above. A pressure oil supply device configured by a load pressure bleed-off valve 62 that becomes

[0017]

[Operation] When the directional control valve 5 is operated from the neutral position to the pressure oil supply position to supply the pump discharge pressure oil to the actuator 6, the load pressure of the actuator 6 directs the spool 15 of the pressure reducing valve unit 3 to the first position. Therefore, the pressure in the load pressure detection path 27 slowly rises, the discharge amount of the variable displacement hydraulic pump 1 slowly increases, and the actuator 6 does not suddenly operate. Pressure reducing valve section 5
When the spool 15 is at an intermediate position between the second position and the first position, a part of the pump discharge pressure oil flows out to the tank, and the pressure in the load pressure detection path 27 becomes lower than the load pressure, so that the variable displacement hydraulic pump 1 Is smaller than a value commensurate with the load pressure, and the flow rate supplied to the actuator 6 is smaller than the required flow rate due to the meter-in opening area of the directional control valve 5, and the directional control valve 5 is operated by a fine stroke to operate the actuator 6. When performing an inching operation, the speed of the actuator becomes slow, so that a smooth inching operation can be performed. When the spool 15 moves to the first position, the load pressure detection path 2
Since the pressure of 7 becomes equal to the load pressure, the discharge amount of the variable displacement hydraulic pump 1 becomes a value commensurate with the load pressure, and the supply flow rate to the actuator 6 becomes the required flow rate due to the meter-in opening area of the directional control valve 5. In normal operation, the actuator can be moved at a predetermined speed. According to the second aspect of the invention, the meter-in opening area of the directional control valve 5 and the load pressure bleed-off valve 62 are switched according to the magnitude of the operation command, and if the magnitude of the operation command to perform the inching operation is an intermediate value, the meter-in opening is performed. Since the area is small and the load pressure bleed-off valve 62 is at the bleed-off position, the discharge amount of the variable displacement hydraulic pump 1 becomes less than the required flow rate during inching operation, the actuator 6 operates slowly, and inching operability is improved. To do.

[0018]

[Embodiment] A first embodiment of the present invention will be described with reference to FIGS. 2, 3, 4 and 5. It should be noted that the same members as those in the related art have the same reference numerals. The pressure reducing valve section 3 has third and fourth ports 40 and 41 formed between the first port 13 and the second port 14, the third port 40 communicates with the tank 42, and the spool 15 has a third port. A small diameter portion 43 is formed to connect / disconnect 41 and the second port 14.

As shown in FIG. 3, the free piston 30 is formed with a small diameter portion 44 and an oil hole 45 which communicates the small diameter portion 44 with the pressure chamber 31, and the spool 15 has a small diameter portion 4.
4 is formed with a port 46 for communicating and blocking 4 with the third port 40, and a port for communicating a space 47 between the blind hole 29 of the spool 15 and the small diameter portion 44 of the free piston 30 with the small diameter portion 43. 48 is formed, and the second port 14 and the second pressure chamber 11 are always communicated with each other through a gap (throttle) between the spool insertion hole 49 and the spool 15.

Next, the operation will be described. (When the directional control valve 5 is in the neutral position as shown in FIG. 2) The pump discharge passage 24 has the first port 13, the opening 33, the damper throttle 32, the pressure chamber 31, the oil hole 45, and the space as shown in FIG. The portion 47 and the port 48 communicate with the fourth port 41, the fourth port 41 is blocked, and the port 46 is the first port 1.
3 and does not communicate with the space 47. That is, the pump discharge passage 24 communicates with the pressure chamber 31 by the damper throttle 32, and the pressure chamber 31 is blocked.

The spool 15 of the pressure reducing valve 3 is pushed to the right by the load pressure acting on the first pressure chamber 10 (when the spool 23 of the directional control valve 5 is slightly stroked to the right from the position shown in FIG. 2). 15 is a balance position on the way shown in FIG. As a result, the fourth port 41 becomes the second port 14
The pump discharge passage 24 is connected to the first port 13,
The opening 33, the damper throttle 32, the pressure chamber 31, the oil hole 45, the space portion 47, the port 48, the small diameter portion 43, and the second port 14 communicate with each other.
It communicates with the port 40.

For this reason, a part of the pump discharge pressure flows out to the tank 42, so that the load pressure acting on the load pressure detecting passage 27 becomes lower than the load pressure acting on the first pressure chamber 10,
The discharge amount of the variable hydraulic pump 1 becomes smaller than the value commensurate with the load pressure. That is, the flow rate becomes smaller than the flow rate required by the meter-in opening area of the directional control valve 5. This causes the actuator to start moving slowly.

That is, the oil hole 45, the space 47, the port 4
6, the spool 15 of the pressure reducing valve unit 3 by the third port 40
A bleed-off circuit that communicates the pump discharge passage 24 with the tank 42 when a stroke is made in the middle.

As described above, the pressure in the second pressure chamber 11 is the first
Since it is lower than the load pressure of the pressure chamber 10, the spool 15 is pushed further rightward to the full balance position shown in FIG.
As a result, the port 46 is shut off from the third port 40 and the bleed-off circuit is shut off, so that the pressure oil in the pump discharge passage 24 is supplied only to the second port 14.
As in the conventional case, the pressure in the load pressure detection path 27 becomes equal to the load pressure, and the discharge amount of the variable hydraulic pump C corresponds to the load pressure.
That is, the meter-in opening area of the directional control valve is the required flow rate. As a result, the actuator operates at a predetermined speed when a certain time elapses after the movement starts.

Therefore, the spool 23 of the directional control valve 5 is moved to the pressure oil supply position and the neutral position for a short time (a time shorter than the time required for the spool 15 to move from the midway balance position to the full balance position). ), The meter-in opening area of the directional control valve 5 can be made small, and the discharge amount of the variable hydraulic pump 1 can be made smaller than the required flow rate to move the actuator 6 slowly, so that the inching operability is improved. To do.

Although the pressure compensating valve 4 and the directional control valve 5 are provided in one valve block in the above embodiments, they may be provided in different valve blocks.

Next, a second embodiment will be described. As shown in FIG. 6, the spool 23 of the directional control valve 5 is held in the neutral position by the left and right springs 50 and 51, and the left first pressure receiving chamber 5
2 pilot pressure oil is pushed to the right to move to the first pressure oil supply position, and right pilot pressure oil in the second pressure receiving chamber 53 is pushed to the left to move to the second pressure oil supply position. The amount of movement of the spool 23 to the first and second pressure oil supply positions (meter-in opening area) is proportional to the pressure of the pilot pressure oil in the first and second pressure receiving chambers 52 and 53.

The hydraulic pilot valve 54 supplies the pressure oil discharged from the pilot hydraulic pump 55 to the first and second pressure receiving chambers 52 and 5 described above.
3 has first and second pressure reducing valve portions 56 and 57 to be supplied to the first and second pressure reducing valve portions 56.
Is connected to the first pressure receiving chamber 52, and the outlet port of the second pressure reducing valve portion 57 is connected to the second pressure receiving chamber 53 by the second pilot circuit 59.

The first and second pressure reducing valve portions 56, 57 are held at positions for blocking the inlet port and the outlet port, and when the operating lever 60 is operated in one direction (direction of arrow a) from the neutral position A, the first pressure reducing pressure is obtained. The inlet port and the outlet port of the valve portion 56 communicate with each other to output pilot pressure oil to the first pilot circuit 58, and the pressure is proportional to the operation stroke of the operation lever 60.

When the operating lever 60 is operated in the other direction (the direction of arrow b), pilot pressure oil having a pressure proportional to the operating stroke is output to the second pilot circuit 59 as described above.

Operation lever 6 of the hydraulic pilot valve 54
The relationship between the operation stroke of 0 and the output pilot pressure is as shown in FIG. 7, for example. In other words, the pilot pressure in the operation stroke L ₁ of the first intermediate P _1, the pilot pressure P ₂ in the second intermediate operation stroke L _2, a third intermediate operating stroke L ₃ at the pilot pressure P _3, the maximum operating pilot pressure becomes P ₄ stroke L _4. (P ₁ <
P ₂ <P ₃ <P ₄ ) A dead zone may be provided so that the pilot pressure is not output when the operation lever 60 is slightly stroked from the neutral position A.

On the other hand, the spool 23 of the directional control valve 5 becomes the pilot pressure is P ₁ and the pressure oil supply position, the meter opening when a minimum the meter opening area at that time, sequential pilot pressure rises and P _2, P ₃ or less Area increases,
The maximum pilot pressure P ₄ maximizes the meter-in opening area.

The load pressure detection path 27 is connected to a bleed-off circuit 61, and a load pressure bleed-off valve 62 is provided in the bleed-off circuit 61, and the load pressure bleed-off valve 62 is at the first cutoff position E. It can be switched between the intermediate bleed-off position F and the second cutoff position G.
Is held at the first shut-off position E by the pilot pressure receiving portion 64.
When the pilot pressure supplied to P becomes P ₂ , the spring 6
Against 3, the intermediate bleed-off position F is reached, and the pilot pressure is moved to the second cutoff position G where P ₃ is reached.

The pilot pressure receiving portion 64 is connected to a high pressure detecting circuit 65, and the high pressure detecting circuit 65 is connected to the first and second pilot circuits 58 and 59 via the first and second check valves 66 and 67. Further, it is connected to the tank 69 through the throttle 68.

Next, the operation will be described. (The operating lever 60 of the hydraulic pilot valve 54 is at the neutral position A
time). The pilot pressure output from the hydraulic pilot valve 54 is zero, and the spool 23 of the directional control valve 5 is in the neutral position by the left and right springs 50 and 51. High voltage detection circuit 6
Since the pressure of 5 is zero and the pilot pressure of the pilot pressure receiving portion 64 is zero, the load pressure bleed-off valve 62 is at the first cutoff position E by the spring 63, and the bleed-off circuit 6
1 is cut off, and the discharge amount of the variable hydraulic pump 1 becomes the set minimum discharge amount.

(Operating lever 60 of hydraulic pilot valve 54
Is operated in one direction (direction of arrow a) by stroke L ₁ ). The hydraulic pilot valve 54 has a first pilot circuit 58.
The pilot pressure P ₁ is outputted to the spool 23 of the directional control valve 5 to the right to reach the first pressure oil supply position, and the meter-in opening area thereof is minimized.

On the other hand, the pilot pressure P ₁ is the high pressure detection circuit 6
5 is supplied to the pilot pressure receiving portion 64, but the load pressure bleed-off valve 62 is a spring 63 and the first shut-off position E.
The bleed-off circuit 61 is shut off, and the load pressure in the load pressure detection circuit 27 is held at the pump directional control valve 26.
And the discharge amount of the variable hydraulic pump 1 increases as the load pressure increases. This operation continues until the operating lever 60 is operated to the stroke L ₂ and the pilot pressure becomes P ₂ .

(Operating lever 60 of hydraulic pilot valve 54
When operating stroke L _{2 in} one direction). The pilot pressure of the first pilot circuit 58 becomes P ₂ , the spool 23 of the directional control valve 5 moves further to the right to increase the meter-in opening area, and the pilot pressure of the pilot pressure receiving portion 64 becomes P _2. The load pressure bleed-off valve 62 becomes the intermediate bleed-off position F, and the bleed-off circuit 61
Communicates with the tank through the throttle 70.

As a result, a part of the load pressure of the load pressure detection circuit 27 flows out (bleeds off) into the tank and the load pressure supplied to the pump adjusting directional control valve 26 becomes lower than the actual load pressure. The discharge amount of the variable hydraulic pump 1 becomes smaller than the discharge amount corresponding to the actual load pressure.

That is, the discharge amount of the variable hydraulic pump 1 becomes smaller than the required flow rate of the directional control valve 5 according to the meter-in opening area.

As a result, the flow rate supplied to the actuator 6 is reduced, so that the actuator 6 operates at a very low speed and the inching operability is improved. At this time, the spool 15 constituting the pressure reducing valve portion 3 of the pressure compensating valve 4 moves slowly, so that the load pressure also rises slowly, and this and the above-mentioned bleed-off of the load pressure are combined with each other to achieve inching operability. Is significantly improved.

In this operation, the operation lever 60 is moved to the stroke L.
_The operation is continued up to ₃ until the pilot pressure reaches P ₃ .

(Operating lever 60 of hydraulic pilot valve 54
Is operated in one direction by stroke L ₃ ). The pilot pressure of the first pilot circuit 58 becomes P ₃ , the spool 23 of the directional control valve 5 moves further to the right to further increase the meter-in opening area, and the pilot pressure receiving portion 64.
Pilot pressure becomes P ₃ and load pressure bleed-off valve 6
2 becomes the second shutoff position G, and the bleed-off circuit 61 shuts off from the tank.

As a result, the load pressure of the load pressure detection circuit 27 becomes the actual load pressure, so that the discharge amount of the variable hydraulic pump 1 becomes a discharge amount commensurate with the actual load pressure, and the meter-in opening area of the directional control valve 5 becomes smaller. Depending on the required flow rate.

This operation is continuously performed until the pilot pressure reaches P ₄ by operating the operating lever 60 up to the maximum stroke L ₄ .

As described above, since the bleed-off valve 62 is switched between the first and second shutoff positions and the intermediate bleed-off position in accordance with the operation stroke of the operation lever 60 of the hydraulic pilot valve 54, the meter-in opening of the directional control valve 5 is performed. When the area has an intermediate size, a part of the load pressure of the load pressure detection circuit 27 is bleed off, the discharge amount of the variable hydraulic pump 1 is reduced, and the flow rate supplied to the actuator 6 is the meter-in opening area of the directional control valve 5. The flow rate becomes smaller than the flow rate required by the spool 15 and its operation is the spool 15 that constitutes the pressure reducing valve portion 3 of the pressure compensation valve 4.
Inching operability is excellent because it is not related to the stroke.

That is, in the first embodiment, a part of the load pressure is bleed off by the stroke of the spool 15 constituting the pressure reducing valve portion 3 of the pressure compensating valve 4, and the stroke of the operating lever 60 of the hydraulic pilot valve 54 is changed. Even if it is between L ₂ and L _3, the spool 15 moves with the passage of time and a part of the load pressure does not bleed off, so that the operating lever 60 is set between the neutral position A and the operating strokes L ₂ and L _3. When alternately operating in time, the actuator 6 is slowly operated to improve inching performance.

However, when the operation lever 60 is held between the operation strokes L ₂ and L ₃ for a long time, the spool 15 does not stroke and bleeds off as described above, and the discharge amount of the variable hydraulic pump 1 becomes actual. The discharge amount corresponds to the load pressure, the actuator 6 operates quickly, and the inching property deteriorates.

On the other hand, according to the second embodiment, the operating lever 60 of the hydraulic pilot valve 54 is moved to the operating stroke L ₂
When it is operated between L ₃ and L ₃ , a part of the load pressure can be bleed off regardless of the stroke of the spool 15, so the inching property can be improved.

In the case of the second embodiment, the pressure compensating valve 4
It is possible to adopt a structure in which the spool 15 forming the pressure reducing valve section 3 does not move slowly, for example, a structure in which the pressure chamber 31 is not formed as shown in FIG. 8, or as shown in FIG. Alternatively, a general pressure compensating valve that is pushed by the load pressure in the closing direction to match the primary pressure to the load pressure may be used.

Next, when a plurality of directional control valves 5 are provided and pressure oil is supplied to a plurality of actuators 6, an embodiment in which pilot pressure is received by the pilot pressure receiving portion 64 of the load pressure bleed-off valve 62 is shown in FIG. It will be described with reference to FIGS. 11 and 12. As shown in FIG. 11, the block main body 71 of each directional control valve 5 is overlapped and connected to communicate each first tank port 21 and each second tank port 22 with each other, and the block 72 is connected to one valve main body 71. The first tank port 21 and the second tank port 22 are communicated with each other through the oil hole 73 of the spool 2 in the case 74 attached to both end surfaces of each valve body 71.
The first and second pressure receiving chambers 52 and 53 are formed by projecting both end portions of 3.

As shown in FIG. 12, the first and second oil holes 80, 8 are provided in the respective valve bodies 71 at positions near both ends in the spool longitudinal direction.
1 is formed in each case, the 1st check valve 82 which connects this 1st oil hole 80 to each 1st pressure receiving chamber 52 is each provided in each one case 74, and each 2nd oil hole 81 is each 2nd.
A second check valve 83 communicating with the pressure receiving chamber 53 is provided in each of the other cases 74.

Each of the first oil holes 80 communicates with the oil hole 84 of the block 72, and each of the second oil holes 81 communicates with the oil hole 84 of the block 72. The oil hole 80 and each second oil hole 81 communicate with each other, and the oil hole 84 of the block 74 thereof communicates with the tank 86 via the throttle 85.

That is, the first and second check valves 82, 83
6 corresponds to the first and second check valves 66 and 67 in FIG. 6, the throttle 85 and the tank 86 correspond to the throttle 68 and tank 69 in FIG. 6, and the oil hole 84 corresponds to the high pressure detection circuit 65 in FIG. .

The oil hole 84 of the block 72 is connected to the pilot pressure receiving portion 64 of the load pressure bleed-off valve 62.

Next, the operation will be described. When the operating lever 60 of one hydraulic pilot valve 54 is operated to output the pilot pressure to the first pilot circuit 58, the pilot pressure is supplied to the first pressure receiving chamber 52 and pushes the spool 23 to the right to move the first pressure oil. The supply position. At the same time, the pilot pressure in the first pressure receiving chamber 52 flows into the first oil hole 80 from the first check valve 82, flows into the oil hole 84 of the block 72 from the first oil hole 80, and the load pressure bleed-off valve 62. It is supplied to the pilot pressure receiving section 64 of.

When the operating lever 60 of the hydraulic pilot valve 54 is returned to the neutral state and the first pilot circuit 58 is communicated with the tank from the above-mentioned state, the pressure in the first pressure receiving chamber 52 is lowered and the spool 23 is moved to the neutral position by the spring 51. At the same time, the pressure oil in the oil hole 84 of the block 72 is throttled 85
And flows into the tank 86, the pressure in the oil hole 84 decreases, and the pilot pressure receiving portion 6 of the load pressure bleed-off valve 62
The pressure in 4 also drops. The second pilot circuit 59
The same applies when the pilot pressure is output to.

By doing so, it is sufficient to provide one load pressure bleed-off valve 62 for a plurality of directional control valves 5, and a body for installing the first and second check valves 82 and 83 is unnecessary. Therefore, the cost can be reduced, and the installation location of the first and second check valves is not required, so that the whole can be made compact.

Further, in the case of the directional control valve 5 for supplying pressure oil to the actuator which does not need to be inched, FIG.
As shown in FIG. 3, the plug 77 is press-fitted into the pressure oil introduction hole 75 of the body 74 or the oil hole 76 that connects the first and second oil holes 80 and 81 of the valve body 71 with the first and second check valves 82 and 83. And block it.

In the second embodiment described above, the spool 23 of the directional control valve 5 is switched by the pilot pressure from the hydraulic pilot valve 54, but as shown in FIG. 14, the electromagnetic proportional switching is performed by the current output from the electric lever device 90. The valve 91 may be switched to supply pilot pressure to the first and second pressure receiving chambers 52 and 53 of the spool 23, or the spool 23 of the directional control valve 5 may be switched by the electromagnetic proportional solenoid 92 as shown in FIG. Current is supplied from the electric lever device 90 and the proportional solenoid 9 of the load pressure bleed-off valve 62 is turned on.
3 may be supplied. 94 is a diode.

That is, the directional control valve 5 has a meter-in opening area proportional to the magnitude of the operation command, and the load pressure bleed-off valve 62 may be switched according to the magnitude of the operation command.

[0062]

According to the first aspect of the invention, when the directional control valve 5 is operated from the neutral position to the pressure oil supply position to supply the pump discharge pressure oil to the actuator 6, the pressure reducing valve section 3 is caused by the load pressure of the actuator 6. Since the spool 15 slowly moves toward the first position, the pressure in the load pressure detection path 27 slowly increases, the discharge amount of the variable displacement hydraulic pump 1 slowly increases, and the actuator 6 rapidly operates. There is nothing to do.

Further, when the spool 15 of the pressure reducing valve unit 5 reaches the intermediate position between the second position and the first position, a part of the pump discharge pressure oil flows out to the tank, and the pressure in the load pressure detecting passage 27 becomes higher than the load pressure. The discharge amount of the variable displacement hydraulic pump 1 becomes smaller than a value commensurate with the load pressure, the supply flow rate to the actuator 6 becomes smaller than the required flow rate due to the meter-in opening area of the directional control valve 5, and the spool 15 becomes When it moves to the 1 position, the pressure of the load pressure detection path 27 becomes equal to the load pressure, and the discharge amount of the variable displacement hydraulic pump 1 becomes a value commensurate with the load pressure. The required flow rate depends on the opening area. Therefore, when the actuator 6 is inching operated by operating the directional control valve 5 with a fine stroke, the speed at which the actuator starts to move becomes slow, so that a smooth inching operation can be performed, and when the actuator 6 is moved to the first position, the directional control valve 5 is moved.
The required flow rate depends on the opening area of the actuator, and the actuator can be operated at a predetermined speed.

According to the second invention, the meter-in opening area of the directional control valve 5 and the load pressure bleed-off valve 62 are switched according to the magnitude of the operation command, and the magnitude of the operation command to perform the inching operation is set to an intermediate value. Then, the meter-in opening area is small and the load pressure bleed-off valve 62 is at the bleed-off position. Therefore, during the inching operation, the discharge amount of the variable displacement hydraulic pump 1 becomes less than the required flow rate, and the actuator 6 operates slowly, resulting in the inching operation. The property is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a conventional example.

FIG. 2 is a sectional view showing the first embodiment of the present invention.

FIG. 3 is a detailed explanatory view of a pressure reducing valve section.

FIG. 4 is an operation explanatory view of a pressure reducing valve section.

FIG. 5 is an operation explanatory view of a pressure reducing valve section.

FIG. 6 is a sectional view showing a second embodiment of the present invention.

FIG. 7 is a chart showing a relationship between an operation lever stroke and pilot pressure.

FIG. 8 is a sectional view showing another example of the pressure compensation valve.

FIG. 9 is a schematic explanatory view showing another example of the pressure compensation valve.

FIG. 10 is a plan view in which a plurality of directional control valves are superposed.

11 is a sectional view taken along line BB of FIG.

12 is a sectional view taken along line CC of FIG.

FIG. 13 is an explanatory diagram when the pilot pressure is not detected.

FIG. 14 is an explanatory diagram showing another example of operating the directional control valve.

FIG. 15 is an explanatory diagram showing another example of operating the directional control valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Variable displacement hydraulic pump 2 ... Check valve part 3 ... Pressure reducing valve part 4 ... Pressure compensation valve 5 ... Directional control valve 6 ... Actuator 9 ... Spool 10 ... First pressure chamber 11 ... Second pressure chamber 12 ... Spring 13 ... 1st port 14 ... 2nd port 15 ... Spool 16 ... Pump port 27 ... Load pressure detection circuit 31 ... Pressure chamber 32 ... Damper throttle 42 ... Tank 52 ... First pressure receiving chamber 53 ... Second pressure receiving chamber 54 ... Hydraulic pilot valve 60 ... Operation lever 61 ... Bleed-off circuit 62 ... Load pressure bleed-off valve 64 ... Pilot pressure receiving part 72 ... Block 80 ... First oil hole 81 ... Second oil hole 84 ... Oil hole.

Claims (6)

[Claims] 1. A variable displacement hydraulic pump 1 whose discharge amount is controlled by a load pressure of a load pressure detection path 27, a pressure compensating valve 4 including a check valve portion 2 and a pressure reducing valve portion 3, and a pump discharge to an actuator 6. A check valve unit 2 is provided with a directional control valve 5 for supplying pressure oil, and the check valve unit 2 connects the pump discharge passage 24 of the variable displacement hydraulic pump 1 and the pump port 16 of the directional control valve 5 to each other.
The pressure reducing valve section 3 is pushed toward the first position where the pump discharge passage 24 and the load pressure detection passage 27 communicate with each other by the load pressure of the actuator 6, and the weak spring 12 and the load pressure are provided. The spool 15 is provided with the spool 15 that is closed to the pump discharge passage 24 and the load pressure detection passage 27 by the load pressure of the detection passage 27 and that is pushed toward a second position that pushes the spool 9 of the check valve portion 2 in the closing direction. 15 is a bleed that moves slowly from the second position to the first position, and at a position intermediate between the second position and the first position, a part of the pressure oil from the pump discharge passage 24 flows out to the tank. A pressure oil supply device having an off circuit. 2. The pressure reducing valve section 3 communicates with a first pressure chamber 10 and a pump discharge passage 24, through which a load pressure flows in to push the spool 15 toward a first position, through a damper throttle 32, and a spool. The pressure chamber 31 that pushes the spool 15 toward the second position and the load pressure detection path 27 communicate with each other through the throttle to connect the spool 15 to the second position.
The second pressure chamber 11 that is pushed toward the position is provided, and the spool 15 is provided.
Is in the second position, the pressure chamber 31 and the load pressure detection passage 27 are shut off, and when the spool 15 is at an intermediate position between the second position and the first position, the pressure chamber 31 communicates with the tank 42 and the load pressure detection passage 27, The pressure oil supply device according to claim 1, wherein the pressure chamber 31 communicates with the load pressure detection passage 27 when the spool 15 is in the first position. 3. A variable displacement hydraulic pump 1 whose discharge amount is controlled by the load pressure of the load pressure detection path 27, and a pump discharge pressure oil which is switched from a neutral position to a pressure oil supply position by an operation command to the actuator 6. The directional control valve 5 that supplies the meter-in opening area of which is proportional to the operation command.
And a pressure compensating valve 4 which is pushed in the opening direction by the pump discharge pressure and is closed in the closing direction by the load pressure of the actuator 6 to make the primary side pressure a pressure commensurate with the load pressure, and is connected to the load pressure detection path 27. Bleed-off circuit 61
The load pressure bleed-off valve 62, which is provided in the bleed-off circuit 61, has a bleed-off position when the magnitude of the operation command is an intermediate magnitude and a shut-off position when the magnitude of the operation command is other than the above. A pressure oil supply device composed of 4. A variable displacement hydraulic pump 1 whose discharge amount is controlled by the load pressure of the load pressure detection path 27, and a hydraulic pilot valve 54 which outputs a pilot pressure of a pressure proportional to the operation stroke of the operating lever 60. The pilot pressure switches the neutral position to the pressure oil supply position to supply pump discharge pressure oil to the actuator 6, and the directional control valve 5 whose meter-in opening area is proportional to the pressure of the pilot pressure and the opening direction by the pump discharge pressure. Pressure compensating valve 4 which is pushed by the load pressure of the actuator 6 in the closing direction to make the primary side pressure equal to the load pressure, and a bleed-off circuit 61 connected to the load pressure detection path 27.
And a load pressure bleed-off valve 62 which is provided in the bleed-off circuit 61 and which is in a bleed-off position when the pilot pressure is an intermediate pressure and is in a shut-off position when the pilot pressure is other than the intermediate pressure. A pressure oil supply device composed of 5. The directional control valve 5, wherein a spool 23 is fitted into a valve body 71, and the spool 23 is slid to a pressure oil supply device at a neutral position by a spring and pilot pressure in a pressure receiving chamber. The valve main body 7 of the directional control valve 5 is superposed and connected, and the oil holes which are mutually connected to the respective valve main bodies 71 and the check valves which communicate the respective oil holes with the pressure receiving chamber are respectively provided, and the oil holes are connected to the load. The pressure oil supply device according to claim 4, which is connected to the pilot pressure receiving portion 64 of the pressure bleed-off valve 62. 6. The pressure compensating valve 4 is composed of a check valve 2 and a pressure reducing valve 3, and the check valve portion 2 connects a pump discharge passage 24 of a variable displacement hydraulic pump 1 and a pump port 16 of a directional control valve 5.・
The pressure reducing valve unit 3 is pushed toward the first position where the pump discharge passage 24 and the load pressure detecting passage 27 communicate with each other by the load pressure of the actuator 6, and the weak spring 12 and the load 9 are provided. The pump discharge passage 24 and the load pressure detection passage 27 are shut off by the load pressure of the pressure detection passage 27, and the spool 15 is pushed toward the second position for pushing the spool 9 of the check valve portion 2 in the closing direction. The pressure oil supply device according to claim 3, 4 or 5, wherein the spool 15 moves slowly from the second position toward the first position.